That is a challenging subject in almost every country in the world!

Athey's work explores challenging subjects like the relationships between desire, sexuality, and traumatic experience.

The course is notorious as one of the most challenging undergraduate subjects.

Convalescing after a series of operations, and about to turn 30, she began looking for a challenging subject for her first book.

QM is a challenging subject for several reasons:

Put your hands together for a director who pulls off a challenging subject with élan.

Fred Newton Scott saw rhetoric as an intellectually challenging subject.

Mr. Rowland could prove a challenging subject at the moment.

The museum could not have started with a more vital and challenging subject than biodiversity.

Agriculture is without doubt the most complex and challenging subject of negotiation in this round.